How can I convert from PDF to JPG without colours changing?

[MorgZ]

I am trying to convert PDFs to images but when I run the command the colours seem to change in the resulting image. The most obvious is that a dark blue colour #0040CS (R0 G64 B197) gets mapped to #004B8E (R0 G75 B142) - using Firefox colour picker tool on the resulting image.

The command I am using is:

"convert test.pdf -resize 340x500 test.jpg"

I have tested this with/without the resize and changing the output file type (jpg / gif / tif). I have also seen if I can reduce the brightness to negate some of the difference in colour. If it helps it looks like the resulting image might be a little bit saturated (just to my eye).

I have had a good search through the forum and on Google and have read that it might be todo with some of the following:

- colorspace
- ghostscript colour translations (I read there is a parameter which can be added to delegates.xml "-dUseCIEColor")

If anyone could give me any guidance here it would be much appreciated as I am not really too sure how I can rectify this issue.

Thanks in advance.

Dave

[fmw42]

is your pdf using cmyk?

what do you get from

identify -verbose imagename


you may need to use profiles to get good color conversion

[MorgZ]

Thanks for the quick reply!

I am fairly certain the PDFs are CMYK.

Using the identify -verbose imagename command I get the following:

Code: Select all

Image: b90c6b87c1ad464c54f18efc3164ee9f2bc072de.jpg
  Format: JPEG (Joint Photographic Experts Group JFIF format)
  Geometry: 340x240
  Class: DirectClass
  Type: ColorSeparation
  Endianess: Undefined
  Colorspace: CMYK
  Channel depth:
    Cyan: 8-bits
    Magenta: 8-bits
    Yellow: 8-bits
    Black: 8-bits
  Channel statistics:
    Cyan:
      Min: 0 (0)
      Max: 255 (1)
      Mean: 219.688 (0.86152)
      Standard deviation: 40.8306 (0.16012)
    Magenta:
      Min: 0 (0)
      Max: 255 (1)
      Mean: 215.184 (0.843859)
      Standard deviation: 38.7639 (0.152015)
    Yellow:
      Min: 0 (0)
      Max: 255 (1)
      Mean: 165.958 (0.650815)
      Standard deviation: 65.3878 (0.256423)
    Black:
      Min: 0 (0)
      Max: 255 (1)
      Mean: 203.226 (0.796964)
      Standard deviation: 73.4102 (0.287883)
  Total Ink Density: 400%
  Colors: 31794
  Rendering-intent: Undefined
  Resolution: 28x28
  Units: PixelsPerInch
  Filesize: 158kb
  Interlace: None
  Background Color: white
  Border Color: #DFDFDF
  Matte Color: grey74
  Dispose: Undefined
  Iterations: 0
  Compression: JPEG
  Quality: 100
  Orientation: Undefined
  JPEG-Colorspace: 4
  JPEG-Sampling-factors: 1x1,1x1,1x1,1x1
  Signature: bc5401da0f7eb113926f9ae30a0cc9ffc11d35de8175195bdc8e07f044108a05
  Tainted: False
  User Time: 0.010u
  Elapsed Time: 0:02
  Pixels per second: 80kb
  Version: ImageMagick 6.2.5 02/13/06 Q16 file:/usr/share/ImageMagick-6.2.5/doc/index.html

I have done further searching and found a few mentions of LCMS which apparently helps matching colours?

Doing a ./configure command shows:

Code: Select all

LCMS              --with-lcms=yes               no

Do I need to change that "no" to "yes" and if so how would I go about that? I have checked with yum and it seems "lcms" is installed on my machine.

I have also had a read up on color profiles but I have no idea how you actually create or get hold of one, only how you can use them with ImageMagick once you have them.

Any further help much appreciated.

[fmw42]

try

convert -colorspace RGB image.pdf image.jpg